Target Pruning and Cutting off a branch

Trees recover most rapidly from large cuts if they are smooth and do not damage the branch collar. If the branch is large, remove the bulk of it first to minimize the weight of what will fall last. First, an undercut is made, sawing to about a quarter of the way into the branch from the underside. This partial cut stops the bark tearing down the trunk if the branch accidentally breaks. Second, cut squarely from the top of the branch about 5 cm beyond the undercut (further away from the trunk) until the branch falls away - the cut should be made to the same level as the undercut. The finishing cut can the be made by following the line of the branch collar from top to bottom . Generally, the line of the cut is approximately 90 degrees to the branch bark ridge.

(above) Note first cut is an undercut and second is a top cut a little distance from the first.

(above) the same area, third and final cut must be smooth. Cut just beyond the branch collar at an equal and opposite angle to that made by the bark ridge on the main stem.

Below is a photo of a cut to remove included bark :

This is a weak point of trees and shrubs. Bark is embedded between opposing branches, creating a structurally weak point. It is best to eliminate these branches as soon as they are noted. If not, as the tree enlarges in diameter and weight, the tree is likely to split at this weak point.

In cutting much larger branches that could potentially be problematic in terms of where it will fall, a wedge can first be made to determine the direction of the fall :

Ref : RHS pruning and training manual pg. 12, 22

Scarification trial

Many seeds such as acacias have very hard seed coats and require a physical method to allow water to enter the seed and break dormancy. Such a process is called scarification. This can sometimes be done with sandpaper, using nutcrackers or nicking with a knife depending on the type of seed. Soaking in hot (not boiling water) for up to 48 hours is another method. Seeds must be sewn directly after the soaking period and must not be allowed to dry otherwise they die.

This trial was to compare germination rates of Acacia verticillata and Dianella tasmanica when seeds had been scarified by soaking in hot water for 24 hours compared with seed that had been given no prior treatment.

10 seeds of treated and 10 seeds of non-treated A. verticillata were sewn in different punnets. The same was done for D. tasmanica. This occured on the 23rd April.

Photos of A. verticillata punnets taken on 19th May, about 4 weeks later, with top punnet containing treated seeds and bottom punnet non-treated :

After 6 weeks (non-scarified on left and scarified on right) :

Note the strike rate for scarified seed is 8 out of 10, whilst non-scarified is 2 out of 10.

This shows that germination rates are higher when Acacia verticillata has been scarified.

At 4 and 6 weeks no Dianella tasmanica had germinated, as is expected with the time it normally takes to germinate.

reference : RHS propagating plants pg 53-4

leaf bud cuttings

Most Camellias can be propagated from leaf bud cuttings of current season's growth that has begun to firm (ie. semi-ripe cuttings, where the base of the cutting is quite hard and the tip of the cutting is still actively growing and thus still quite soft). These cuttings include the leaf and axillary bud or node. This allows for many cuttings to be taken from the same stem. Cuttings are made the same size to allow ease of handling by ensuring most cuttings take root at roughly the same time. These are placed into the prop. mix after each cutting has been dabbed in rooting hormone gel, leaving the bud on the surface of the mix. Flower buds are pinched out. With bottom heat, rooting usually takes 6-12 weeks. 

We also took some leaf bud cuttings from a potted Ficus elastica cultivar. Using secateurs, a cut was made straight across a stem just above a node - a rule of thumb is about the distance of the width of the stem itself - and about 2.5cm below the same node. Keeping the waxy side of the leaf outermost, the leaf was rolled to form a cylinder, secured with a rubber band and placed into the prop. mix after a dab in semi-hardwood rooting hormone gel. The lead node should sit on the surface of the mix. The cutting can be supported with a small cane through the rolled leaf as shown above. This is kept in the misting house under humid conditons until rooted. 

Larger leaf Camellia varieties can be handled in a similar manner as shown below : 

Ref : RHS propagating plants, pg. 95, 120

Root Cuttings

A limited range of plants, particularly ones that naturally produce suckers from the roots can be propagated from root cuttings. In this activity, I propagated Wisteria sinensis, whilst others propagated Acanthus mollis, using this technique.

Appropriate cuttings were located by digging carefully with a trowel around the base of the selected Wisteria vine, ensuring no damage was done to the larger root system. Root cuttings were of pencil-thickness, although thinner root cuttings are also just as successful. The thinner the cutting the longer they should be. Cuttings are best done in autumn or winter when the plant is dormant. The cuttings are then lightly washed in water to remove soil.

Each root section is cut into approx. 5cm sections. To make sure the cuttings are inserted the right way up, the base is cut horizontally and the top at and angle.

The cutting is then dabbed in semi-hardwood rooting hormone and then inserted into the propagation mix.

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The cuttings are then watered thoroughly and placed into the misting house on top of a capillary sand bed with bottom heat.

Ref : RHS Propagating Plants, pg. 23-4, 158

Below is a photo of Acanthus mollis root cuttings prepared on 19th May and photographed on the heating and misting beds almost a month later on 17th June :

Cold moist stratification

Some tree seeds have a physiological dormancy which can be broken by certain levels of cold or heat. Such seeds need to be treated by stratification.

In this exercise, we used seeds from Betula pendula, Acer buegeranum, Zelkova serrata - all deciduous trees native to the Northern hemisphere. We chill seeds in a refrigerator at temperature between 0 - 5 degrees celsius, to mimic the passing of winter and to gain a more even germination. Seeds need to be kept moist and so are sealed in plastic bags before being placed in the refrigerator.

Betula pendula catkins were harvested from the TAFE garden.

Samaras from Acer and Zelkova spp. were collected from the Botanic Gardens.

The seed-raising mix used consisted of equal parts of pasteurised sand, cocopeat, perlite, combined with trichodry and mini-osmocote.

A low punnet was filled with this mix and tamped down gently but firmly.

Betula seeds were scattered as a thin layer across the mix and then covered lightly with the same mix.

Zelkova and Acer seeds were placed gently by hand in the mix and again covered lightly.

These were then watered and placed in plastic bags and refrigerated as previously mentioned.

Betula pendula stratification period was from 22/4/09 - 15/5/09 (25 days)

Zelkova serrata and Acer buergeranum from 22/4/09 - 14/6/09 (55 days)

After each stratification period, punnets were removed from fridge and placed on heating and misting beds.

Betula pendula seedlings all had excellent germination rates and were pricked out on 30/6/09 :

Ref :RHS propagating plants, pg. 54

Disease 6 - Leaf twist virus in grapefruit

Citrus trees are best grown in warm to hot climates, with mild winters. Some varieties of citrus, however, can be successfully grown in colder climates, including this grapefruit variety, "Wheeney." 

The above photo shows a viral infection, with symptoms of yellow mottling on leaves and puckering, although this could be also due to a combination of frost and wind damage. Viral infections in citrus are untreatable and like with all other viral infections, prevention by buying specimens propagated from virus-tested and/or more resistant material is the key. 

Ref : Judy McMaugh, pg. 73-4

Disease 5 - Daphne Virus

Daphnes grow best in cool areas and need soils rich in organic matter and slightly acidic. They prefer semi-shade and a cool, moist root run, so mulching is important. Daphne odora, the most common species, suffers from a number of viruses. These viruses are untreatable, but more resistant varieties have been released, termed "High health" plants. 

Symptoms of viral illness are shown in the specimens above, found in the Royal Botanic Gardens. They can include yellow blotches, irregular streaks, dead flecks, twisting or puckering. Flowers are often small, distorted and green. The whole plant may be stunted. 

Ref : Judy McMaugh, pg. 107